• Alexei Starovoitov's avatar
    perf, bpf: allow bpf programs attach to tracepoints · 98b5c2c6
    Alexei Starovoitov authored
    introduce BPF_PROG_TYPE_TRACEPOINT program type and allow it to be attached
    to the perf tracepoint handler, which will copy the arguments into
    the per-cpu buffer and pass it to the bpf program as its first argument.
    The layout of the fields can be discovered by doing
    'cat /sys/kernel/debug/tracing/events/sched/sched_switch/format'
    prior to the compilation of the program with exception that first 8 bytes
    are reserved and not accessible to the program. This area is used to store
    the pointer to 'struct pt_regs' which some of the bpf helpers will use:
    +---------+
    | 8 bytes | hidden 'struct pt_regs *' (inaccessible to bpf program)
    +---------+
    | N bytes | static tracepoint fields defined in tracepoint/format (bpf readonly)
    +---------+
    | dynamic | __dynamic_array bytes of tracepoint (inaccessible to bpf yet)
    +---------+
    
    Not that all of the fields are already dumped to user space via perf ring buffer
    and broken application access it directly without consulting tracepoint/format.
    Same rule applies here: static tracepoint fields should only be accessed
    in a format defined in tracepoint/format. The order of fields and
    field sizes are not an ABI.
    Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
    Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    98b5c2c6
bpf.h 10.6 KB